Public Works and Development Services » Forestry » Emerald Ash Borer

Emerald Ash Borer

Emerald Ash Borer (EAB), Agrilus planipennis Fairmaire, is an invasive beetle native to Asia that was first discovered in southeastern Michigan near Detroit in the summer of 2002. The adult beetles feed on ash foliage but cause little damage. The larvae (the immature stage) feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients. EAB probably arrived in the United States on solid wood crating material carried in cargo ships originating in its native Asia. EAB has been reported as established in Ohio (2003), Indiana (2004), Maryland (2006), Illinois (2006), Pennsylvania (2007), West Virginia (2007), Wisconsin (2008), Missouri (2008), Virginia (2008), Minnesota (2009), and New York (2009). Since its discovery, EAB has: 1) killed tens of thousands of ash trees in southeastern Michigan, with tens of millions more lost in the other states mentioned above. 2) Caused regulatory agencies and the United States Department of Agriculture (USDA) to enforce quarantines and fines to prevent potentially infested ash trees, logs or hardwood firewood from moving out of areas where EAB has been reported. 3) Cost municipalities, property owners, nursery operators and forest products industries tens of millions of dollars. The EAB infestation was discovered in a declining ash tree by River Forest Public Works on the 1200 block of Franklin Avenue on August 11, 2008. Based on that discovery we can assume that EAB arrived in River Forest 3-4 years before the tree showed signs of decline, or between 2004 and 2005.

Forestry staff became aware of EAB in 2002 while attending annual training seminars. At that time it was a relatively new problem affecting areas in and around Detroit. All public works employees were trained to identify signs and symptoms of EAB infestations in ash trees

Impacts on River Forest

The Village of River Forest has approximately 8,000 parkway trees of which approximately 275 ash trees remain. The Village of River Forest is proud of its urban forest and takes its management quite seriously. A Tree City USA community since 1998, River Forest strives to maintain a diverse parkway tree population. It is important that this EAB Management Plan is used as a guideline and that it remains flexible, taking economic times, new circumstances and the most current research into consideration. Research on EAB and how to manage this insect is in a constant state of change. By being diligent, yet open-minded, about managing this insect we hope that this management plan helps to create a more diverse and healthy urban forest that provides the greatest benefit to all those that live in and visit our community.

Management Recommendations - Public Property Trees

Our management plan will consist of a number of procedures that will focus on maintaining a healthy urban forest and diversifying our overall tree inventory. Due to the rapid spread of EAB, early and quick action will be vital to the operation of a successful program. Our goal will be to act as soon as possible and as budgetary constraints allow. Public property ash trees are assessed during routine tree trimming and drive-by inspections and are deemed “Healthy”, “Treated” or “Infested”.

Healthy Trees: These trees do not show two or more signs or symptoms of infestation or greater than 50% canopy decline. They also appear to be healthy and do not need any action at this time. Removal will not be necessary until EAB infestation or any other causes of decline are present.

Treated Trees: The Village has chosen to treat approximately 225 parkway ash trees to manage EAB losses in areas where monocultures exist. These trees will be treated biannually for as long as funds allow and monitored for signs of EAB infestation. Removal will not be necessary until EAB infestation or any other causes of decline are present.

Residents may choose to fund a treatment application on a non-treated parkway tree but are required to obtain permission from the Village Forester with the understanding that the Village has the right to remove the tree for any justifiable reason. Payment for treatment will be the responsibility of the homeowner. Homeowners must also be aware that treatments are anticipated to be required for the life of the tree and must be done annually or biannually based on the treatment chosen.

Infested Trees: The Illinois Department of Agriculture (IDOA) has established guidelines for recognizing EAB infested trees. There are eight identifiable signs and symptoms that a tree may be infested with EAB (crown dieback, epicormic sprouting or suckers, bark splits, D-shaped exit holes in the bark, S-shaped larval galleries under the bark, the presence of larvae, woodpecker damage to the outer bark, and presence of adult beetles). If two or more of these signs and symptoms are present or the tree is at least 50% dead, we will consider the tree infested and it will be removed. In addition, if the tree is determined to be in decline (by our certified Forestry staff), and/or the tree is exhibiting splitting or decay/hollowness the tree will be removed. No treatment will be allowed on these trees. The tree will be removed by the Village as time and budget allow.

Management Recommendations - Private Property Trees

Healthy ash trees can be treated to prevent EAB infestations. Residents that elect to treat their ash trees should have them inspected by a certified arborist to determine if the tree is healthy and treatment is the best option. Residents can find a local certified arborist here.
Useful information for homeowners, including a “treatment decision guide” can be found here. If a resident thinks that a private property tree may be infested with EAB, they should contact a certified arborist to inspect the tree in question. If the tree is confirmed to exhibit signs or symptoms of EAB, it should be removed within 30 days.

Residents who are concerned that trees on others’ private property may pose health or safety concerns to their own property may request an inspection by Village staff. Due to manpower limitations, these trees will be inspected on an “as time permits” basis. Private property trees that are identified by Village staff as “infested” in this management plan will be required to be removed within 30 Days of notification as required by local code 6-8-3: ABATEMENT OF NUISANCES.

Material Handling: In order to minimize the spread of EAB through the infested material, the IDOA began asking any company or municipality handling ash debris to sign an official IDOA Compliance Agreement. This agreement requires that the company or municipality properly dispose of any ash wood in compliance with the IDOA requirements. River Forest first signed this agreement in 2009.

Reforestation: It is critical that we continue to pursue diversified species tree planting on public property and provide proper species planting information to residents so as to mitigate the impact of extensive tree loss. Not every tree removed can be replaced due to several factors including underground and overhead utilities and location of other private property and public property trees. The Village of River Forest will continue to pursue diverse tree planting throughout the Village where possible.

Public Education: The Village of River Forest will continue to update our residents with all of the latest information regarding EAB via the Village’s website. It is very important to provide our residents with the latest information to help make educated decisions regarding their private property trees.

Program Future: This management plan will remain flexible and will be amended when new information, research or technology becomes available.

Signs and Symptoms

  • Crown Dieback: Dieback of the upper and outer crown begins to occur after multiple years of EAB larval feeding. Trees begin to show dead branches throughout the canopy, thus resulting in leaf loss. Foliage in the top of the tree may be thin and discolored.
  • Epicormic Sprouting: Stressed trees will attempt to grow new branches and leaves where they still can. Trees may sucker excessively both at the base of the tree and on the trunk, often just below where the larvae are feeding.
  • Bark Splits: Vertical splits in the bark are caused due to callus tissue that develops around larval galleries. Larval galleries can be seen beneath bark splits.
  • D-Shaped Emergence Holes: As adults emerge from under the bark they create an emergence hole – 1/8 inch in diameter and D-shaped.
  • S-Shaped Larval Galleries: As larvae feed under the bark they wind back and forth, thus creating galleries that are packed with frass sawdust and follow a serpentine pattern.
  • Larvae: Cream colored, slightly flattened, and have pincher-like appendages at the end of their abdomen. Mature larvae reach 1 ½ inches in length and all larvae are found feeding beneath the bark.
  • Adults: Metallic green in color and are 3/8 – 1/2 inch in length and 1/8 inch in width. Adults are flat on the back and rounded on their underside.
  • Woodpecker Damage: Damage occurs from woodpeckers drilling through the bark of trees to forage for larvae located under the bark. White patches of bark are observed on trunks and branches and feeding is typically evident higher in the tree where EAB prefers to infest initially.
  • Decline: Refers to progressive loss of vigor and health, not to any specific disease or disorder. Trees decline for many reasons, sometimes as the result of a single disease or damaging environmental factor but often as a result of several environmental and biotic factors acting in concert or in sequence. Decline results from the action of stressing factors over periods of years.

A visual guide to the conditions described above can be found here.